Heating device

ABSTRACT

A heating device includes a housing, a primary induction coil, a controller circuit, and a secondary induction coil. The housing retains a camera lens. The primary induction coil is positioned proximate the housing and generates a magnetic field in response to receiving electrical power from a power supply. The controller circuit is in electrical contact with the primary induction coil and controls the electrical power delivered to the primary induction coil. The secondary induction coil overlays the primary induction coil and receives the magnetic field from the primary induction coil and generates heat. The secondary induction coil is in direct contact with a windshield of a vehicle and heats the viewing window when the primary induction coil receives the electrical power.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to EP Application No. 18213507.9, whichwas filed on 18 Dec. 2018.

TECHNICAL FIELD

The present disclosure relates generally to a heating device that clearscondensation from a viewing window of a camera.

BACKGROUND

Typical heating devices require electrical terminals and wiring attachedto a windshield or cover-glass. United States Patent ApplicationPublication Number 2006/0171704 A1 describes a heating element forheating a transparent camera lens cover that includes electricalterminals in contact with a surface of the transparent camera lenscover. Other applications describe a heating element positioned on alens holder, and resilient contacts used to heat a camera lens.

SUMMARY OF THE DISCLOSURE

The present disclosure proposes to solve the above mentioned problem byproviding a heating device comprising a housing configured to retain acamera lens, a primary induction coil positioned proximate the housingand configured to generate a magnetic field in response to receivingelectrical power from a power supply, a controller circuit in electricalcontact with the primary induction coil configured to control theelectrical power delivered to the primary induction coil, and asecondary induction coil overlaying the primary induction coilconfigured to receive the magnetic field from the primary induction coiland generate heat. The secondary induction coil is in direct contactwith a windshield of a vehicle and defines a viewing window throughwhich the camera lens views a surrounding area. The secondary inductioncoil heats the viewing window when the primary induction coil receivesthe electrical power.

According to other advantageous features of the present disclosure:

the primary induction coil surrounds an optical axis of the camera lens;

the controller circuit includes a low-Q resonant circuit in electricalcommunication with the primary induction coil;

a temperature of the secondary induction coil is controlled by adjustinga voltage applied to the primary induction coil;

a temperature of the secondary induction coil is controlled by adjustinga frequency of a signal delivered to the primary induction coil;

the secondary induction coil is comprised of a first layer of resistivematerial and a second layer of low-Curie point ferrite;

the secondary induction coil is located between glass layers of thewindshield;

the secondary induction coil is located on an inner surface of thewindshield;

the secondary induction coil is located on an outer surface of thewindshield;

the secondary induction coil is formed of a conductive material having agreater electrical resistance relative to the primary induction coil;

the secondary induction coil is characterized as segmented, whereinadjoining segments are formed of materials having a different electricalconductivity from one another;

a distance between the primary induction coil and the secondaryinduction coil is in a range from 0.0 mm to 10.0 mm;

a number of windings on the primary induction coil is at least one;

a number of windings on the secondary induction coil is at least one;

the secondary induction coil has a thickness in a range from 1.0 μm to1000 μm;

the secondary induction coil has a width in a range from 0.1 mm to 10mm.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is now described by way of example with referenceto the accompanying drawings in which:

FIG. 1 is an exploded perspective view of a heating device according toan embodiment of the disclosure;

FIG. 2 is a section view of the heating device of FIG. 1 ;

FIG. 3 is a section view of a portion of the heating device of FIG. 2 ;

FIG. 4 is a schematic of the heating device of FIG. 1 illustrating acontroller circuit.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a heating device 10 for a windshield 20 and/or acover-glass according to an embodiment of the present disclosure will bedescribed with reference to the figures. FIG. 1 is an explodedperspective view illustrating the heating device 10, hereafter referredto as the device 10. The device 10 includes a housing 12 configured toretain a camera lens 14. The housing 12 may be formed of any material,such as a polymeric material, a ceramic, or a metal. The housing 12 mayhave a circular cross section or may have any other cross section, suchas a rectilinear cross section. The housing 12 may include an imager 15used to render an image of a surrounding area. The camera lens 14defines a field-of-view 16 and an optical axis 18 as illustrated in FIG.1 . The housing 12 may be mounted on a front of a vehicle, on sides of avehicle, on a rear of a vehicle, or mounted in the interior of thevehicle at a location suitable for the camera to view the area aroundthe vehicle through the windshield 20. In the examples illustratedherein, the housing 12 is mounted inside the vehicle with the viewthrough the windshield 20.

The device 10 also includes a primary induction coil 22 positionedproximate the housing 12 and configured to generate a magnetic field 24in response to receiving electrical power 26 from a power supply 28. Thepower supply 28 may be a direct-current (DC) power supply 28, or may bean alternating-current (AC) power supply 28. In the examples illustratedherein the power supply 28 is an AC power supply 28. The primaryinduction coil 22 surrounds the optical axis 18 of the camera lens 14and may also surround a portion of the housing 12. A number of windings30 (e.g., wires, conductive traces, etc.) on the primary induction coil22 is at least one and are preferably wound onto a ferromagnetic core 32(e.g. iron, ferrites, etc.). It will be appreciated that the number ofwindings 30 will increase with the increasing size of the area requiredto be heated. It will also be appreciated that the ferromagnetic core 32may be omitted (i.e., an air core coil) depending on packaging andweight constraints. A single winding 30 (i.e. a single wire) of theprimary induction coil 22 may be any diameter, and in the examplesillustrated herein, preferably has the diameter in a range from 0.2 mmto 1.0 mm. The windings 30 may be formed of any electrically conductivematerial, such as copper alloys or aluminum alloys and may include adielectric layer on a surface of the windings 30.

The device 10 also includes a controller circuit 34 in electricalcontact with the primary induction coil 22. The power supply 28 may beseparate or integral to the controller circuit 34, and in the examplesillustrated herein, the power supply 28 is integral to the controllercircuit 34. The controller circuit 34 is configured to control theelectrical power 26 delivered to the primary induction coil 22. Thecontroller circuit 34 may include a processor (not shown) such as amicroprocessor or other control circuitry such as analog and/or digitalcontrol circuitry including an application specific integrated circuit(ASIC) for processing data as should be evident to those in the art. Thecontroller circuit 34 may include a memory (not shown), includingnon-volatile memory, such as electrically erasable programmableread-only memory (EEPROM) for storing one or more routines, thresholds,and captured data. The one or more routines may be executed by theprocessor to perform steps for determining the electrical power 26delivered to the primary induction coil 22 based on signals received bythe controller circuit 34 from the primary induction coil 22, asdescribed herein.

The device 10 also includes a secondary induction coil 36 overlaying theprimary induction coil 22. The secondary induction coil 36 is configuredto receive the magnetic field 24 from the primary induction coil 22,thereby generating heat 38. The magnetic field 24 from the primaryinduction coil 22 induces an electrical current in the secondaryinduction coil 36. The induced electrical current in the secondaryinduction coil 36 causes the secondary induction coil 36 to increase intemperature because the secondary induction coil 36 is formed of amaterial that has an electrical resistance. The electrical resistance ofthe secondary induction coil 36 resists the flow of electrical currentwithin the secondary induction coil 36, which generates the heat 38(also known as Joule heating or Ohmic heating). It will be appreciatedthat no wire connections exist between the primary induction coil 22 andthe secondary induction coil 36. This has the technical benefit ofreducing a size and complexity of the overall assembly. The secondaryinduction coil 36 also surrounds the optical axis 18 and is in directcontact with the windshield 20 of the vehicle. In the exampleillustrated in FIG. 1 , the secondary induction coil 36 is located on aninner surface 42 of the windshield 20. In an alternative embodiment thesecondary induction coil 36 may be located on an outer surface 43 of thewindshield 20.

The secondary induction coil 36 defines a viewing window 40 throughwhich the camera lens 14 views the surrounding area. That is, an innerdiameter of the secondary induction coil 36, as illustrated in FIG. 1 ,creates a “window” through which light rays may pass to the camera lens14 and imager 15. The secondary induction coil 36 heats the viewingwindow 40 and removes condensation (e.g., fog, ice, etc.) when theprimary induction coil 22 receives the electrical power 26 from thecontroller circuit 34. A heating rate and a maximum temperature iscontrolled to inhibit a thermal shock to the windshield 20, and also toprevent an unsafe surface temperature of the windshield 20 for humancontact.

FIG. 2 is a section view of the device 10 and illustrates an embodimentwhere the secondary induction coil 36 is located between glass layers 44of the windshield 20. A distance 46 between the primary induction coil22 and the secondary induction coil 36 is preferably in a range from 0.0mm to about 10.0 mm. The distance 46 primarily impacts a coupling of theprimary induction coil 22 and the secondary induction coil 36.

The number of windings 30 on the secondary induction coil 36 is at leastone, and may be increased to achieve a specific temperature profileapplied to the windshield 20. The windings 30 on the secondary inductioncoil 36 may be a single flat winding 30 that may be deposited using athick-film ink, for example. The secondary induction coil 36 asillustrated in FIG. 2 has a thickness 48 in the range from about 1 μm toabout 1000 μm. The thickness 48 may be adjusted based on the type ofmaterial comprising the secondary induction coil 36, and based on afrequency 50 of the electrical power 26 delivered to the primaryinduction coil 22. In an embodiment, the secondary induction coil 36 hasa thickness 48 of 400 μm and is formed of a material with a low relativemagnetic permeability (e.g., silver, aluminum, etc.). In anotherembodiment, the secondary induction coil 36 is formed of a materialhaving higher relative magnetic permeability (e.g., iron) having athickness 48 of 15 μm. The thickness 48 may also be reduced byincreasing the frequency 50 of the of the electrical power 26 deliveredto the primary induction coil 22. The secondary induction coil 36 has awidth 49 in a range from about 0.1 mm to 10 mm, and preferably has thewidth 49 of about 5 mm due to packaging constraints on the windshield20. It will be appreciated that the width 49 of the secondary inductioncoil 36 affects the heat transfer to the windshield 20. The width 49 maybe user defined depending on a desired heating profile for thewindshield 20.

FIG. 3 is a magnified view of a portion of the device 10 of FIG. 1 . Thesecondary induction coil 36 is preferably comprised of a first layer 52of resistive material that dissipates the power transmitted by themagnetic field 24, and a second layer 54 of low-Curie point ferrite.When the secondary induction coil 36 reaches a Curie point temperature(e.g. approximately 90 degrees Celsius for a Mn—Zn ferrite at 8 μm-9 μmthickness 48), the magnetic permeability of the second layer 54 isdecreased, thereby reducing the induced heating of the secondaryinduction coil 36. This reduction of the induced heating of thesecondary induction coil 36 changes a resonant-frequency of a controlcircuit 56, the benefit of which will be described in more detail below.Preferably, the secondary induction coil 36 is formed of a conductivematerial having a greater electrical resistance than that of the primaryinduction coil 22. The first layer 52 and the second layer 54 may alsohave a protective coating (not specifically shown) applied to theirexposed surfaces to improve a durability of the layers.

Referring back to FIG. 1 , the secondary induction coil 36 may becharacterized as segmented 58, wherein adjoining segments 58 are formedof materials having a different electrical conductivity from oneanother. That is, a first segment may have a relatively low electricalresistance thereby emitting a relatively low quantity of heat 38,wherein a second segment in contact with the first segment may have ahigher electrical resistance compared to the first segment, therebyemitting a larger quantity of heat 38 than the first segment. Thissegmentation 58 has the technical benefit of enabling a specific heatingprofile on the windshield 20. For example, preferentially heatingcorners of a rectangular viewing window 40 where the corners are agreater length away from the optical axis 18 compared to a side of therectangular viewing window 40 that may be closer to the optical axis 18.It will be appreciated that other patterns of segmentation 58 arepossible based on a geometry of the viewing window 40.

FIG. 4 is a schematic diagram of the device 10 illustrating thecontroller circuit 34. The controller circuit 34 preferably includes alow-Q resonant control circuit 56 in electrical communication with theprimary induction coil 22. A Q-factor (i.e., quality factor) of anelectronic circuit is a parameter that describes the resonance behaviorof a harmonic oscillator or resonator. The low-Q factor is indicative ofan overdamped system that does not resonate or oscillate. The low-Qresonant control circuit 56 has the technical benefit of improvedtemperature control in the secondary induction coil 36. It will beappreciated that the values of capacitors C1 and C2 (not specificallyshown) may be selected to achieve the desired resonant-frequency todrive the secondary induction coil 36 and produce the desired heat 38.The temperature of the secondary induction coil 36 may be controlled byadjusting a voltage 62 applied to, and/or adjusting the frequency 50 ofa signal delivered to, the primary induction coil 22 through the MOSFETsM1 and M2 (not specifically shown) and through the power supply 28. Thecontroller circuit 34 is configured to monitor an impedance of theprimary induction coil 22, which is directly related to the temperatureof the secondary induction coil 36, and controls the voltage 62 and/orfrequency 50 (e.g. 40 kHz) to maintain proper operation of the controlcircuit 56. This method of temperature measurement has the technicalbenefit or eliminating a separate temperature sensor mounted to thewindshield 20.

The invention claimed is:
 1. A heating device comprising: a housingconfigured to retain a camera lens; a primary induction coil positionedproximate the housing and configured to generate a magnetic field inresponse to receiving electrical power from a power supply, the primaryinduction coil surrounding an optical axis of the camera lens; acontroller circuit in electrical contact with the primary induction coilconfigured to control the electrical power delivered to the primaryinduction coil; and a secondary induction coil overlaying the primaryinduction coil and configured to receive the magnetic field from theprimary induction coil and generate heat; wherein the secondaryinduction coil is disposed within a windshield of a vehicle or on aninner surface of the windshield and defines a viewing window throughwhich the camera lens views a surrounding area; wherein the secondaryinduction coil directly heats the viewing window of the windshield whenthe primary induction coil receives the electrical power; and wherein atemperature of the secondary induction coil is controlled by adjusting avoltage or a frequency of a signal applied to the primary inductioncoil.
 2. The heating device in accordance with claim 1, wherein thecontroller circuit includes a low-Q resonant circuit in electricalcommunication with the primary induction coil.
 3. The heating device inaccordance with claim 1, wherein the secondary induction coil iscomprised of a first layer of resistive material and a second layer oflow-Curie point ferrite.
 4. The heating device in accordance with claim1, wherein the secondary induction coil is located between glass layersof the windshield.
 5. The heating device in accordance with claim 1,wherein the secondary induction coil is formed of a conductive materialhaving a greater electrical resistance relative to the primary inductioncoil.
 6. The heating device in accordance with claim 1, wherein thesecondary induction coil is characterized as segmented, whereinadjoining segments are formed of materials having a different electricalconductivity from one another.
 7. The heating device in accordance withclaim 1, wherein a distance between the primary induction coil and thesecondary induction coil is in a range from 0.0 mm to 10.0 mm.
 8. Theheating device in accordance with claim 1, wherein a number of windingson the primary induction coil is at least one.
 9. The heating device inaccordance with claim 1, wherein a number of windings on the secondaryinduction coil is at least one.
 10. The heating device in accordancewith claim 1, wherein the secondary induction coil has a thickness in arange from 1 μm to 1000 μm.
 11. The heating device in accordance withclaim 1, wherein the secondary induction coil has a width in a rangefrom 0.1 mm to 10 mm.
 12. The heating device in accordance with claim 1,wherein the temperature of the secondary induction coil is controlled byadjusting the frequency of the signal applied to the primary inductioncoil.
 13. A camera system comprising: a housing comprising: a cameralens; and an imager configured to receive light via the camera lens andrender an image of a surrounding area of the camera system; a primaryinduction coil: proximate an end of the housing that is opposite theimager, surrounding an optical axis of the camera lens, and configuredto generate a magnetic field in response to receiving electrical powerfrom a power supply; a controller circuit configured to control theelectrical power; and a secondary induction coil: within a windshield ofa vehicle or on an inner surface of the windshield, overlaying theprimary induction coil, defining a viewing window within or on thewindshield through which the camera lens views the surrounding area, andconfigured to receive the magnetic field from the primary induction coiland directly heat the viewing window of the windshield when the primaryinduction coil receives the electrical power, wherein a temperature ofthe secondary induction coil is controlled by adjusting a voltageapplied to the primary induction coil or by adjusting a frequency of asignal delivered to the primary induction coil.
 14. The camera system ofclaim 13, wherein the secondary induction coil is further configured toremove condensation from the viewing window.
 15. The camera system ofclaim 13, wherein the secondary induction coil comprises: a first layerof resistive material configured to dissipate power transmitted by themagnetic field; and a second layer of low Curie point ferrite.
 16. Thecamera system of claim 15, wherein the secondary induction coil isfurther configured to reduce the heat generated by the secondaryinduction coil once the secondary induction coil reaches a Curie pointtemperature.
 17. The camera system of claim 16, wherein: the controllercircuit comprises a resonant control circuit in electrical communicationwith the primary induction coil; and the reduction of the heat generatedby the secondary induction coil causes a resonant frequency of theresonant control circuit to be changed.
 18. The camera system of claim13, wherein the secondary induction coil is located between glass layersof the windshield.
 19. The camera system of claim 13, wherein thetemperature of the secondary induction coil is controlled by adjustingthe frequency of the signal applied to the primary induction coil. 20.The camera system of claim 13, wherein the controller circuit is furtherconfigured to monitor an impedance of the primary induction coil todetermine a temperature of the primary induction coil.